JPH0731996A - Waste water treating method - Google Patents

Abstract

PURPOSE:To stably and efficiently remove an org. matter and a nitrogen compd. by disposing an aerobic and an anaerobic fixed bed type reactor at the post stage of a fluidized bed type reactor, treating a waste water, then bringing the waste water into contact with ozone to remove simultaneously remaining org. matter and nitrogen compd. CONSTITUTION:In the waste water treating method of the org. industrial waste water, a sludge treated water and the city sewerage in which large bulk of the org. industrial waste water inflows, the aerobic fixed bed type reactor 11 and the anaerobic fixed bed type reactor 13 are disposed at the post state of the fluidized bed type reactor 3 using a microorganisms-immobilized carrier. Then, after executing the treatment at both the reactors 11 and 13, moreover, an ozone-contacting tank 24 is being disposed, and the ozone from an ozone- generating device 25 is brought into contact with a biologically treated water to remove simultaneously the org. matter and the nitrogen compd. remaining in the biologically treated water. In this way, the org. matter difficult to be decomposed, which can not be removed by the biological treatment, are removed thoroughly together with the NO2-N remaining slightly, and the COD of the treated water is improved and the treatment is stabilized.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an ammonia compound which is a reducing nitrogen compound, such as organic industrial wastewater, sludge treated water, and municipal sewage into which a large amount of organic industrial wastewater flows, in an amount of 50 to 100 mg / l or more. In the treatment of contained wastewater, pollutants (BOD) displayed by biological oxygen demand contained in the wastewater, organic carbon compounds in the wastewater (TO
C), pollutants (CO
D) and a method for advanced treatment of wastewater for stable and efficient removal of nitrogen compounds.

[0002]

2. Description of the Related Art Conventionally, as a method for biologically removing pollutants (BOD) and nitrogen compounds such as ammonia compounds contained in municipal sewage at the same time, it has been proposed to use the Badenfor (BOD) method.
ardenpho) method, (JL Barnard, W.
ater Wastes Engg. , 33,197
4), or the A / O method and A ₂ / O method described in Japanese Patent Publication No. 54-24774.

Further, as a modified method of the A ₂ / O method described in Japanese Patent Publication No. 61-17558, there is known a method of incorporating a rotating disk for immobilizing microorganisms in a nitrification tank.

In these methods, BOD is mainly due to oxidative decomposition of aerobic microorganisms, and ammonia compounds are
It is oxidized to nitrate nitrogen by nitrifying bacteria.

Further, Japanese Patent Publication No. 54-24774 discloses a fluidized bed reactor in which activated sludge is present.
Tank, aerobic 1 tank, anaerobic 2 tanks, and aerobic 2 tanks
Various aerobic and anaerobic levels are controlled by using the oxidation-reduction potential (ORP) as an index, and granulated blast furnace slag, carbon fine powder, etc. are used as a carrier for immobilizing activated sludge, and BOD and nitrogen Biological methods for the removal of compounds, phosphorus compounds have been described.

ORP is superior as a measure of aerobic and anaerobic levels in comparison with dissolved oxygen concentration (DO) and nitrogen compound concentration, which have been used as indicators until then, and controls nitrification reaction and denitrification reaction. Thus, the nitrogen compound can be efficiently removed.

In addition to the biological treatment process, sewage and organic wastewater are treated by biological treatment when the concentration of organic substances and nitrogen compounds that are difficult to decompose biologically is high. Later, various chemical oxidation processes have been applied.

Ozone, chlorine, hydrogen peroxide and the like are major oxidizing agents used in such chemical oxidation treatment.

In particular, a method of using hydrogen peroxide and an iron salt such as ferrous sulfate in combination is called the Fenton method, and the generated hydroxyl radical has a strong oxidizing power. It is widely known as a method for treating industrial wastewater with a high concentration of compounds (for example, Aiko-Se Kobo, No. 17,
1989).

[0010]

A conventional biological nitrogen removal process for municipal wastewater, such as the A ₂ / O method, which has a concentration of ammonia compounds of about 20 to 50 mg / l, is not suitable for comparison. It is possible to biologically oxidize ammonia compounds to nitrate nitrogen (NO ₃ —N).

However, the concentration of BOD and COD is high, and the amount of ammonia compound is 50 mg / l to 100 mg / l.
It is quite difficult to apply it as it is to the industrial wastewater contained above and the municipal sewage and sludge treated water into which a large amount of industrial wastewater is flowing.

That is, when the wastewater contains a high concentration of organic substances and ammonia compounds, nitrous acid (NO ₂ —N) generation type oxidation proceeds in the reactor and NO ₂ —N tends to accumulate. Strongly, 1 mg of NO ₂ —N is measured as COD, which is 1.14 mg.
There is a concern that OD will rise.

Furthermore, in order to prevent the NO ₂ -N-generated oxidation organic loading and reactor aerobic degree control of a very important issue, in a manner that is conventional, NO ₂ -N type Preventing oxidation is quite difficult.

The above is described, for example, in "Wat.
s. 1990, Vol 24, No 3, pp. 303
―312 pointed out.

That is, the ammonia compound is 80 mg /
1 mg of artificial wastewater containing 0.5 mg of dissolved oxygen (DO)
In a fluidized bed reactor maintained at 1 / l, NO ₂ -N was 60 when treated with a reactor residence time of 4 days.
It reported that it accumulated mg / l, and concluded that NO ₂ —N-generated oxidation proceeded even when the dissolved oxygen (DO) was low.

Further, an experiment was conducted in which the COD of the inflow water was varied, and it was reported that the organic matter load affects the NO ₂ -N forming type oxidation.

As described above, in the conventional biological nitrogen removal process, when treating wastewater having a high organic matter concentration and further containing 50 mg / l or more of ammonia compounds, the treatment time becomes very long. , Equipment cost becomes huge.

Also, many unclear points remain regarding the shadow control of the organic matter load on the nitrification reaction and the control method of the aerobic level.

Further, in order to efficiently oxidize reducing nitrogen compounds in municipal wastewater to nitrate nitrogen (NO ₃ -N), a reactor in which activated sludge is present has a redox potential (O).
RP) is used as an index, and a process using a fluidized bed reactor that uses granulated blast furnace slag, carbon fine powder or the like as a carrier for immobilizing activated sludge is considered to be efficient.

This is because the ORP is easier to control the nitrification reaction as compared with the DO, and the nitrifying bacteria can be maintained at a high concentration in the reactor because the immobilized carrier is used.

By the single treatment process of this fluidized bed reactor, reducing nitrogen compounds in municipal wastewater can be efficiently and stably removed.

However, when the single treatment process of this fluidized bed reactor is also applied to the treatment of wastewater containing high concentrations of organic substances and ammonia compounds, the organic compounds of the wastewater cause biological oxidation of ammonia compounds up to NO ₃ -N. May be disturbed.

Further, there is a method of combining such a biological treatment method and a chemical oxidation treatment method such as Fenton oxidation method. For example, as shown in "Aikonosesho", No. 17, 1989, The Fenton oxidation method uses C in raw water.
It is recognized that it has an effect on OD removal and NO ₂ —N oxidation.

However, in the case of treatment of wastewater having a high concentration of reducing nitrogen compounds, NO ₂ --N accumulates in the treated water by a biological treatment method such as the conventional activated sludge method, and thus NO ₂
-The amount of reagents consumed for N-oxidation increases, the running cost increases, and the method becomes extremely uneconomical.

Therefore, when the biological treatment method and the chemical oxidation treatment method such as the Fenton oxidation method are combined, the ammonia compound is NO ₃ --N in the biological treatment process.
Oxidized or removed by denitrification by reducing it to nitrogen gas and adding N in biologically treated water.
It is important that no O ₂ --N remains.

The present invention improves the conventional treatment method for treating wastewater containing organic matter and high concentration of nitrogen as described above to eliminate problems and to stably and efficiently treat organic matter The purpose is to establish an advanced treatment method for wastewater to remove nitrogen compounds.

[0027]

DISCLOSURE OF THE INVENTION The present invention provides a fluidized bed reactor using a microorganism-immobilized carrier and an aerobic immobilization in the treatment of an organic wastewater containing a reducing nitrogen compound in an amount of 50 mg / l or more. After performing the three-stage biological treatment of the bed type reactor and the anaerobic fixed bed type reactor,
This is a high-level treatment method for wastewater, which is characterized by removing organic substances and nitrogen compounds in the wastewater at the same time by bringing ozone into contact with the treated water.

The fluidized bed reactor uses granulated blast furnace slag, silica sand, activated carbon, plastics, cristobalite, carbon fine powder, etc. as a carrier for immobilizing microorganisms, and the oxidation-reduction potential of the reactor is set to wastewater. -50 to + 50m suitable for oxidative decomposition of low molecular weight organic compounds
It is a process of supplying air, and / or oxygen-enriched air, and / or oxygen to perform aeration so as to control in the range of V (gold-silver / silver chloride electrode reference).

The aerobic fixed bed type reactor uses saddle type ceramics, which uses granulated blast furnace slag as a main material, silica-alumina type ceramics, etc., as a carrier for immobilizing microorganisms, and the ORP of the reactor is wastewater. Suitable for oxidizing ammonia compounds in NO ₃ -N +
Air and / or oxygen-enriched air, and / or so as to control to 100 mV or more (gold-silver / silver chloride electrode standard)
Alternatively, it is a process of supplying oxygen to perform aeration.

Further, the anaerobic fixed bed type reactor uses saddle type ceramics mainly made of granulated blast furnace slag, silica-alumina type ceramics and the like as a carrier for immobilizing microorganisms, and the ORP of the reactor is used as waste water. Suitable for reducing NO ₃ -N in the atmosphere to nitrogen gas-10
0mV to -150mV (gold-silver / silver chloride electrode standard)
Control so that waste water is added and air and / or oxygen-enriched air and / or oxygen are supplied to perform aeration.

That is, according to the present invention, in a wastewater treatment method of organic industrial wastewater, sludge-treated water, or municipal wastewater into which a large amount of organic industrial wastewater flows, a fluidized bed reactor using a microorganism-immobilized carrier is provided after the fluidized bed reactor. After the aerobic fixed bed type reactor and the anaerobic fixed bed type reactor are installed and treated, an ozone contact tank is further provided to bring ozone into contact with the biologically treated water and to remove organic matter remaining in the biologically treated water. It is characterized in that nitrogen compounds are simultaneously removed.

Blast-furnace granulated slag is preferably used as the microorganism immobilization carrier for the fluidized bed reactor, and saddle type cearamix containing blast-furnace granulated slag as the main raw material is preferably used as the microorganism immobilization carrier for the fixed bed reactor. .

The amount of air and / or oxygen-enriched air and / or oxygen blown into the fluidized bed reactor and the aerobic fixed bed reactor and the anaerobic fixed bed reactor is based on the redox potential (ORP) of the reactor. The amount of ozone supplied to the ozone contact tank is adjusted based on the ultraviolet absorption spectrum of the biologically treated water. An Fe-based amorphous material may be used as a catalyst for the ozone treatment.

[0034]

The fluidized bed reactor is intended to efficiently remove organic substances contained in wastewater.

By using granulated blast furnace slag, silica sand, activated carbon, plastics, cristobalite, fine powder of carbon, etc. as a carrier for immobilizing microorganisms, the sedimentation property of microorganisms is improved and a high concentration can be maintained in the reactor. As a result, the treatment time can be shortened to 1/2 to 1/3 as compared with the case where the immobilized carrier is not used.

Among them, the granulated blast furnace slag contains calcium as a main component, and due to the effect of promoting the aggregation of calcium, the immobilization performance of microorganisms is excellent as compared with other immobilization carriers, and it is the most immobilization carrier. It is desirable.

ORP of the reactor and organic matter of the wastewater (TO
The removal performance of C) has a close relationship as shown in FIGS.

Therefore, the ORP of the fluidized bed reactor
Is maintained at −50 to +50 mV (based on gold-silver / silver chloride electrode), the oxidative decomposition of the low molecular weight organic matter in the wastewater can be sufficiently promoted.

It is effective to keep the ORP of the reactor at +50 mV or more in order to accelerate the oxidative decomposition of the high molecular weight organic matter in the waste water, but NO ₂ -N is accumulated in the treated water and COD is reversed. It is not preferable because it will rise.

When the organic matter concentration in the wastewater is high, the ORP of the fluidized bed type reactor is -50 to +5 in air aeration.
It may be difficult to maintain at 0 mV, and if too much air is used, the activated sludge will be destroyed and fragmented.
It does not settle sufficiently in the sludge settling tank, it flows into the treated water,
The treated water may be deteriorated.

In such a case, a method of supplying oxygen-enriched air and / or oxygen to perform aeration is desirable.

Furthermore, the ORP of the fluidized bed type reactor is
By maintaining at 50 to +50 mV, and preferably at 0 mV, the accumulation of NO ₂ —N can be prevented.

Since NO ₂ -N has an inhibitory action on bacteria decomposing organic substances, it is desirable to prevent accumulation.

The aerobic fixed bed reactor is biologically efficient up to NO ₃ -N by nitrification reaction of nitrogen compounds contained in wastewater, mainly reducing nitrogen compounds such as Kjeldahl nitrogen compounds and ammoniacal compounds. The purpose is to oxidize.

Since the organic matter in the wastewater is sufficiently removed by the fluidized bed reactor in the first stage, the inhibitory effect on the nitrification reaction of the organic matter is small, and the NO ₃ -N forming type nitrification reaction can be efficiently advanced. it can.

Nitrob, which has a slow growth rate, is used as a carrier such as saddle type ceramics, silica-alumina type ceramics and plastics, which are mainly made of granulated blast furnace slag.
By immobilizing nitrifying bacteria such as acter at a high concentration, the NO ₃ —N-producing nitrification reaction can be efficiently advanced.

Particularly, the saddle type ceramics, which is mainly made of granulated blast furnace slag, has calcium as a main component,
Nitrifying bacteria are easily immobilized, and because of the saddle shape, the gas-liquid mixing performance in the fixed bed reactor is excellent, and it is the most desirable as the immobilized carrier for the fixed bed reactor.

Further, the OR of the aerobic fixed bed reactor
By maintaining P at +100 mV (gold-silver / silver chloride electrode standard) or more, reducing nitrogen compounds such as Kjeldahl nitrogen compounds and ammoniacal compounds can be produced by nitrification reaction.
It is possible to efficiently oxidize nitrate nitrogen compounds.

When the concentration of reducing nitrogen compounds in the wastewater is high, the ORP of the reactor is +100 in air aeration.
It may be difficult to maintain mV or higher, and in such a case, aeration may be performed by supplying oxygen-enriched air and / or oxygen.

The anaerobic fixed bed reactor is intended to biologically efficiently reduce NO ₃ -N contained in the aerobic fixed bed reactor treated water to nitrogen gas.

Also in the anaerobic fixed bed reactor, saddle type ceramics, silica-alumina type ceramics and plastics, which are mainly made of granulated blast furnace slag, are used as a carrier for immobilizing microorganisms to enhance denitrifying bacteria with a slow growth rate. By fixing the concentration, the denitrification reaction can proceed efficiently.

Particularly, the saddle type ceramics, which is mainly made of granulated blast furnace slag, has calcium as a main component,
Denitrifying bacteria are also easily immobilized.

Furthermore, the OR of the anaerobic fixed bed reactor
By maintaining P at about −100 mV to −150 mV (gold-silver / silver chloride electrode standard), NO ₃ —N can be biologically and efficiently reduced to nitrogen gas by denitrification reaction. it can.

The method of controlling the ORP of the anaerobic fixed bed reactor is to add the required amount of waste water or methanol in order to give organic substances as hydrogen donors.
Air and / or oxygen-enriched air and / or oxygen are supplied for control in case the ORP falls too low.

For the denitrification reaction, it is usually 30 to 30% higher than the calculated value.
About 40% requires a large amount of organic matter, but if the ORP of the anaerobic fixed bed reactor is maintained at about -100 mV, the organic matter of the wastewater added is 9% as shown in FIG.
It is removed by 0% or more.

Further, although it is an ozone contact tank installed in the latter stage of the anaerobic fixed bed type reactor, oxidation of organic substances and NO ₂ -N remaining in the anaerobic fixed bed type reactor treated water which is difficult to biodegrade It is used to improve the COD removal rate of the treated water by complete oxidation.

Since denitrification is progressing in the fixed-bed reactor treated water, the concentration of NO ₂ —N is 10 mg / l or less except immediately after the start-up, so that the ozone consumption can be reduced. .

Compared with an oxidizer such as hypochlorous acid, ozone has ammoniacal nitrogen (NH ₄
N) hardly reacts with the remaining NO ₂ ―
Economical if you want to remove only N.

Since the hardly decomposable organic substances which are difficult to decompose biologically have a benzene ring in many cases, the degree of decomposition by biological treatment or ozone treatment can be judged by the ultraviolet absorption spectrum. .

For example, when ozone is not detected by the measurement of the ultraviolet absorption spectrum of the fixed bed reactor treated water, it is not necessary to add it, and the biological treated water can be discharged as it is, and the running cost can be reduced.

Also, the amount of ozone added is preferably adjusted by measuring the ultraviolet absorption spectrum of ozone-treated water.

Further, in order to increase the efficiency of ozone oxidation, it is possible to further reduce the running cost by increasing the ozone oxidation efficiency by using a catalyst such as Fe-based amorphous material, iron powder, Ni powder and the like. Is.

Next, examples of the present invention will be described.

[0064]

[Example] A field experiment using actual sewage was conducted at an urban sewage treatment plant into which a large amount of organic industrial wastewater flows. As shown in Table 1, the actual sewage has a BOD of 500 on average.
mg / l, COD average 500 mg / L, ammoniacal nitrogen average 150 mg / l, and it is sewage with high organic matter concentration and ammoniacal nitrogen concentration compared with city sewage.

In the fluidized bed reactor, 3 wt% of granulated blast furnace granulated slag having an average particle diameter of about 60 microns is added as a microorganism-immobilized carrier per reactor volume, and after acclimatization of activated sludge for about 10 days, the fluidized bed is used. The actual sewage was passed so that the treatment time in the mold reactor was 8 to 12 hours.

The ORP of the fluidized bed reactor was controlled by oxygen so as to be maintained at 0 mV.

The aerobic and anaerobic fixed bed type reactors are filled with saddle type ceramics, which is mainly made of granulated blast furnace slag, as a microorganism immobilization carrier, charged with activated sludge in the reactor and circulated for 1 day, After fixing activated sludge to ceramics, the processing time of each reactor is 6
The treated water was passed through the fluidized bed reactor so that the time was reached.

ORP of aerobic fixed bed reactor
Was adjusted to +100 mV by oxygen-enriched air, and the ORP of the anaerobic fixed bed reactor was adjusted to −100 mV by wastewater and oxygen-enriched air.

As the ozone generator, a contact device equipped with a mixer was used in order to supply oxygen to generate ozone, and to bring the treated water and ozone into contact with each other efficiently.

As shown in FIG. 3 and FIG. 4, the ozone supply amount of the ozone contact tank is as shown in FIG.
70 nm). Further, an Fe-based amorphous material was used as a catalyst in order to increase the efficiency of ozone oxidation.

The experimental results are shown in Table 1. From the results in Table 1, the final treated water of this process has a BOD of 10 mg / l.
Below, COD is 50 mg / l or less, NO ₂ —N is N.
D and NO ₃ —N were good at 10 mg / l or less.

From this experimental result, it became clear that the present process can efficiently remove organic matters and nitrogen compounds in the sewage with a total treatment time of about 20 to 24 hours even in the low water temperature period of winter.

[0073]

[Table 1]

[0074]

From the above, the present invention has the following advantages in the treatment of wastewater containing a high concentration of reducing nitrogen compounds such as Kjeldahl nitrogen compounds and ammoniacal compounds and organic substances. .

That is, in the case of such wastewater treatment,
Although there is the inhibition of microorganisms and the control of NO ₂ -N that is a COD source in treated water becomes the most problematic, in this process, the organic matter removal process by the fluidized bed reactor and the aerobic and anaerobic fixed bed reactor are used. Since the nitrogen compound removal process is carried out by means of, the organic substance removal and reducing nitrogen compounds such as ammoniacal nitrogen can be carried out more efficiently than the single biological treatment process by the fluidized bed reactor or fixed bed reactor. Can be removed.

[0076] Further, to remove the NO ₂ -N remaining slightly and persistent organic substances can not be removed by biological treatment, since the provided ozone contact tank downstream, NO ₂ -N
Can be completely removed, the COD of the treated water is improved, and
Can be stabilized.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between ORP of a fluidized bed reactor and treated water quality.

FIG. 2 is a diagram showing the relationship between the ORP of the reactor and the removal rate of organic matter of wastewater.

FIG. 3 is a diagram showing an ultraviolet absorption spectrum of biologically treated water (fixed bed treated water).

FIG. 4 is a diagram showing an ultraviolet absorption spectrum of ozone-treated water.

FIG. 5 is an explanatory diagram showing a method of the present invention.

[Explanation of symbols]

 1 Waste Water Tank 2 Waste Water Pump 3 Fluidized Bed Type Reactor 4 Oxygen Enriched Air Manufacturing Equipment 5 ORP Sensor 6 ORP Controller 7 Sludge Sedimentation Tank 8 Return Sludge Pump 9 Treated Water Tank 10 Transfer Pump 11 Aerobic Fixed Bed Reactor 12 Ceramics Filling Tank 13 Anaerobic fixed bed reactor 14 Ceramics filling tank 15 ORP sensor 16 ORP control device 17 ORP sensor 18 ORP control device 19 Oxygen-enriched air production device 20 Oxygen-enriched air production device 21 Waste water pump 22 Treated water tank 23 Transfer pump 24 Ozone Contact tank 25 Ozone generator 26 Waste ozone treatment device 27 Final treated water

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 3/10 ZAB A 3/30 ZAB A

Claims (6)

[Claims] 1. A method for treating wastewater of organic industrial wastewater, sludge-treated water, or municipal wastewater into which a large amount of organic industrial wastewater flows, in which aerobic fixation is carried out after a fluidized bed reactor using a microorganism-immobilized carrier. After the bed-type reactor and the anaerobic fixed bed-type reactor are installed and treated, an ozone contact tank is further provided to bring ozone into contact with the biologically treated water, and to remove organic substances and nitrogen compounds remaining in the biologically treated water. A wastewater treatment method characterized by simultaneous removal. 2. The wastewater treatment method according to claim 1, wherein granulated blast furnace slag is used as the microorganism-immobilized carrier of the fluidized bed reactor. 3. The wastewater treatment method according to claim 1, wherein saddle-type ceramics made from granulated blast furnace slag are used as the microorganism immobilization carrier of the fixed bed reactor. 4. The amount of air and / or oxygen-enriched air and / or oxygen blown into the fluidized bed reactor and the aerobic fixed bed reactor and the anaerobic fixed bed reactor is set to the redox potential (ORP) of the reactor. The wastewater treatment method according to claim 1, 2 or 3, which is adjusted based on the above. 5. The wastewater treatment method according to claim 1, wherein the amount of ozone supplied to the ozone contact tank is adjusted based on the ultraviolet absorption spectrum of the biologically treated water. 6. The wastewater treatment method according to claim 1, wherein an Fe-based amorphous material is used as a catalyst during ozone treatment.